In the field of communication and signal processing, DC (direct current) offset signifies at least the offset in the DC component of a signal. Although some DC offsets may be introduced intentionally for various purposes, other DC offsets may be undesired results occurred during transmission or signal processing. For example, DC offsets may be introduced during signal processing at a WLAN (wireless local area network) receiver, which may connect a computing device with a network via an access point.
Without limiting the scope of the invention, we describe below the signal processing of a WLAN receiver to illustrate an example of DC offset. Generally, a WLAN receiver may down-convert a radio frequency (“RF”) signal to an intermediate frequency (“IF”) signal, and then down-convert the IF signal to baseband (“BB”) signal. Such receiver structure is also known as super-heterodyne, which may require an additional IF surface-acoustic-wave (“SAW”) filter. To eliminate the IF stage, a direct conversion receiver may directly down-convert an RF signal to a BB signal. This receiver structure may achieve cost reduction by avoiding IF components, such as a SAW filter. However, undesirable, and sometimes significant, direct current (DC) offset may be introduced by a local oscillator and associated leakage.
Undesirable DC offset may affect the quality of processed signals and impact signal transmissions, such as signal transmissions through a wireless receiver.
Therefore, there is a need for a method or a device that reduces or mitigates DC offset, including DC offset in a direct conversion WLAN receiver.